This invention relates generally to roll baling machines typically referred to as "round balers" which form cylindrical bales of crop material and, in particular, to an apron tensioning system for such machines.
Round balers of the expandable chamber type disclosed in U.S. Pat. Nos. 4,343,141 to F. A. Oellig et al and 4,426,833 to W. R. Campbell have included a bale forming apron which is maintained under tension during bale formation by utilizing coil springs or air springs. One drawback of the coil springs disclosed in the Oellig et al patent is that the tension in the apron cannot be quickly and easily released when servicing the baler. Another drawback of these coil springs is that they are bulky and heavy. The air springs disclosed in the Campbell patent overcome these drawbacks but they are costly and require additional frame structure due to the high forces they exert. Furthermore, adjustability of the air springs is limited to decreasing the apron tension only unless an on-board air supply is included.